1. Field of the Invention
The present invention relates to an output circuit, and more specifically, to an output circuit capable of being operated by a wide range of power supply voltages.
2. Description of the Related Prior Art
Various kinds of relays, solenoids and the like are coupled with an output circuit of a programmable controller (hereinafter, referred to as a PC), a numerical control apparatus (hereinafter, referred to as an NC) and the like, and load elements such as these relays, solenoids and the like have various electric specifications with coil voltages of DC 12 V, DC 24 V, DC 48 V, AC 100 V, AC 200 V and the like. To comply with load elements having such a wide variety of characteristics and specifications, the PC and NC are generally provided with output circuits having various characteristics and these output circuits are suitably combined and used in accordance with a combination of the loads.
As described above, although various kinds of output circuits are generally provided for the PC and NC in accordance with the kind of load, a great many kinds of output circuits are required because they are composed of combinations of DC, AC, load voltages and load currents.
Accordingly, the development of an output circuit which can be operated by a wide range of voltages is now underway, to enable a reduction of the number of the output circuits needed. For example, a circuit is available which can be operated by voltages from DC 12 V to DC 24 V or voltages from AC 100 V to AC 200 V and the like.
Note, since many loads composed of TTL's operated by a power supply voltage of DC 5 V are used, the realization of an output circuit which can be operated by voltages ranging from DC 5 V to DC 24 V or from DC 5 V to DC 48 V will greatly reduce the kinds of output circuit modules needed. Conventionally, however, it has been difficult to produce a low cost output circuit which can be operated by this range of voltages.